Vocal fold waveform shape with rich harmonics is what makes speech possible

Evidence

The open/closed cycling of the vocal folds during normal voicing results in roughly triangular pressure peaks, with rests between the triangles if the folds have closed completely. Such a waveform has many harmonics populating the formants (see the next section) and giving the voice richness of tone. The higher harmonics are subject to amplification and suppression by the vocal tract resonances and antiresonances. If the folds produced a sinusoidal wave, speech as we know it could not exist. — Eric J. Heller, Why You Hear What You Hear- An…, 1660

Categorization

• DEFINE: Explains why the glottal waveform must be rich in harmonics, not sinusoidal, for speech to work.
• XREF: Connects to the formant filtering explained in the following section and to the trumpet comparison in ch. 17.